Friday, June 19, 2009

The Spider Web of Scientific Nomenclature, or How I Started With a Shark and Ended Up in Australia by Way of the French Revolution

"Nomenclature is a preface to understanding." Richard Fortey (Trilobite: Eyewitness to Evolution, 2000, p. 29)

In which the blogger concludes that a 1939 coup against the shark genus name Corax may have been unjustified, builds a mountain out of a mole hill, is easily distracted, and considers a Trilby hat.

This post is another in the series I’ve written on scientific names, their science and art.

For children’s birthday parties, my mother often created an enormous spider web out of yarn in a large room. Each strand of yarn began at the doorway and, in its length, often suspended, crisscrossed the room, and ended connected to a little gift. Each partygoer told hold of the end of an individual strand and, then, chaos ensued as each tried to go where the line led, until (it was hoped by all adults present) each child happily secured a party favor.

That spider web game comes to mind when I try to untangle the history behind some scientific names. The labyrinthine process through which some organisms acquired their scientific names continues to challenge me. In trying to retrace steps through that labyrinth, I grab hold of a piece of yarn and follow it, hoping for clarity, some bright, fixed lines, but, instead, I often find complexity, confusion, ambiguity, and, yes, some welcome surprises. The yarn’s inevitably connected to something, or some things, though not always the expected. Perhaps that’s just life.

Following the Strand of Yarn

In a 1939 article, Gilbert Percy Whitley (1903-1975), renowned Australian ichthyologist, renamed the extinct shark genus Corax as Squalicorax. In a previous post, I explored a bit of the taxonomic history of the Squalicorax genus of sharks, prompted by my attraction to their complex fossilized teeth. I was left pondering why Louis Agassiz in 1843 applied the name Corax to the genus of these sharks (Corax is, after all, Latin or Greek for “Raven” – if I understand the messy Web, the same word is used in both Latin and Greek). Somewhat secondarily, I asked why G.P. Whitley had been moved to rename the genus in 1939.

I have his answer for the second question. I now have a copy of Whitley’s 1939 article, a lengthy and somewhat eclectic compilation of data on many different kinds of sharks – mostly, as far as I can tell, living sharks. In this piece, Whitley asserted,

A new name is necessary for the shark called Corax, because Mr. T. Iredale informs me that Agassiz’ name is preoccupied by Corax Ledru (Voy. Ténériffe, ii., 1810, p. 204), a generic name for the Raven. [Taxonomic Notes on Sharks and Rays, by G.P. Whitley, The Australian Zoologist, 1939, p. 240.]

Believing that a genus of bird already had the name Corax (“preoccupied”), he fashioned the new name Squalicorax, incorporating the old (Squalus is Latin for “fish” or “shark”).

Unseating Agassiz

I wonder about the story behind that small piece of Whitley’s 1939 article. Tom Iredale (1880-1972), Australian ornithologist and conchologist, had long been intimately involved in ornithological nomenclature, having spent several years on the nomenclature committee of the British Ornithologists’ Union. Uncovering something like Ledru’s work was, I guess, par for the course for someone like him who probably relished that kind of arcane discovery. His entry in the Australian Dictionary of Biography is revealing. "Gifted with extraordinary bibliographical ability, he enjoyed astounding scientific gatherings by quoting long references from memory."

So, Iredale found a bit of “incriminating” evidence against the Corax shark genus name and brought it to the attention of his ichthyologist colleague, Whitley, who, perhaps, was not reluctant to overthrow one of Agassiz’s names, since apparently he was no stranger to nomenclature controversy. One biographical piece asserts, “His taxonomy revealed confidence and something of his impish nature: his 'little regard for rules of nomenclature' provoked disagreement and displeasure from international colleagues on more than one occasion.”

So the shark genus Corax fell, replaced by Squalicorax.

Loose Ends

What Whitley concluded is straightforward, unambiguous, so, obviously, case closed.

I’m not so sure.

Whitley’s action seems premised on an understanding that two genera, regardless of their marked divergence in their overall taxonomic identification, cannot have the same genus name. I see sense in that, but I’m unclear about how rigorously that rule, if it is one, is actually applied. The International Commission on Zoological Nomenclature, the arbiter for the process of giving scientific names to different kinds of organisms, extinct and extant, apparently doesn’t consider non-duplication to be an inviolate rule. For instance, in a 2009 opinion (#2220), the ICZN ruled that the names for two kinds of insects Hemerobius elegans Stephens, 1836 (for a European brown lacewing) and Hemerobius elegans Guérin-Méneville, 1844 (for a neotropical green lacewing) could be conserved, reasoning that: “Both names are in current use but are placed in different families and unlikely to ever be treated as congeneric in the future.” (“Congeneric” means “of the same genus.”)

Identical genus and species names for lacewings from two different genera . . . . Hmm, maybe, we could have kept Corax for the shark. Would anyone have thought that the shark genus Corax was congeneric with a Corax bird genus?

What else does Whitley’s Squalicorax entry in his article offer for our consideration? Well, might there may be something interesting to discover if we blow off the layer of dust that covers volume II of Voyage aux iles de Ténériffe, La Trinité, Saint-Thomas, Sainte-Croix et Porto-Ricco, . . . . (Voy. Ténériffe), other than how variable the spelling of place names has been?

Not surprisingly, we have at hand the usual bubbly brew of the relevant and interestingly irrelevant. This is the volume that, according to Iredale, showed the genus name Corax was preoccupied. Published in 1810 and written by André Pierre Ledru et al., it reports the natural history findings from a voyage to the Canary Islands and the West Indies in the late 1790s. In this volume, Ledru described a raven-like bird which he spotted on the voyage. With its crossed beak, he named it Corax crucirostra.

(Ledru (1761-1825) merits an aside. He was ordained as a priest when the French Revolution broke out – not a great career path at that moment. But, he did what he had to do in order to survive, ultimately forsaking the priesthood when the Revolution turned against religion, and, in another wise move, getting out of France for awhile by serving as a botanist on the 1796-1798 voyage of discovery.)

Back to the issue at hand, it’s not clear to me whether or how long the name Corax crucirostra was used. A century later (and some 30 years before Whitley), it was clearly considered invalid. In a 1904 article, Robert Ridgway, the Curator of the Division of Birds at the U.S. National Museum (Smithsonian Institution), asserted that Corax crucirostra was one of several synonyms for Corvus leucognaphalus, the latter, according to Ridgway’s entry, having been named in 1800 (yes, it precedes the 1810 publication by Ledru). Under scientific nomenclature, synonyms aren’t names that can be substituted for one another (as common usage would have it), rather they are invalid names and shouldn’t be used. According to Ridgway, Corvus leucognaphalus was this bird’s valid name.

Were Iredale and Whitley simply unaware of Ridgway’s publication? Am I missing something here? I’m coming to believe that there might not really have been any preoccupying of the Corax genus name, after all.

(By the way, nothing has changed in the intervening century. Corvus leucognaphalus is the valid name for the presently extant White-Necked Crow, a bird in serious decline and confined primarily to parts of Haiti and the Dominican Republic.)

Then there’s the small matter of Whitley’s choice of a word. He calls Corax a “generic name for the Raven.” Is he using “generic” as in the “genus name” for that bird? If so, I find that very confusing, since Linnaeus named the Common Raven, Corvus corax – the genus isn’t Corax. Perhaps Whitley meant a “common” or “plain vanilla” name for Raven, which seems right given the definition of “Corax” in Greek and Latin. If so, should the common usage of “Corax” carry weight in an argument against retaining it for the scientific name of a shark genus?

Not that it makes any difference, but, I’m left unconvinced by Whitley’s conclusion that Corax needed to be replaced. Still, I enjoyed spinning the yarn and I’m pretty sure Whitley and Iredale enjoyed their roles.

Other Finds from the Spider Web
My piece of yarn in this spider web of scientific nomenclature, unlike the birthday version, connected me to multiple gifts, not just an explanation of the name change. Whitley and Iredale are impressive figures, each with a substantial body of publications and memorialized in the scientific names of various fish and birds, among other animals.

Then there’s this wonderful group picture from 1950. The inscription on the reverse of this picture reads as follows:

13/3/50. Dear Major Whittell, another for your Rogues' Gallery. Left to right: G.P. Whitley, T.A. Everitt (Hon. Sec. R.Z.S.N.S.W.), A.J. Moran (Cairns, Q. naturalist), Tom Iredale, Alex Chisholm. No woder [sic] the traffic was held up in sydney when this photo was taken a week or two ago. Regards Gilbert P. Whitley

[Permission to post this group picture provided by the National Library of Australia, picture on the Web at: Full citation information provided below.]
Whitley is the grinning one without a hat; Iredale is the one facing the camera head on and smiling. This picture draws me in, capturing a period in time when hats and three-piece suits were de rigueur, though, in this instance, the bare-headed Whitley flouted the convention, perhaps in keeping with his “impish” character. Iredale wore his hat at a charming and cocky angle. There is a confidence in their posture and in the look on their faces. Is Whitley tapping his foot? Impatience?

I’m not sure I can explain fully how and why, but the picture of G.P. Whitley and his colleagues reminds me of another, a very personal one, one of my maternal grandfather.

Each of these pictures captures a moment that is now long gone, yet tantalizingly recent. I know these people and what happened to them. Though the one of my grandfather is probably from a period earlier than 1950, there are essential similarities. The hat and three-piece suit are the fashion. By God, that same confident, cocky air radiates from my grandfather.

His inscription to my mother on the reverse is:
Happy whistling bare foot boy or sumthin'
Your Dad

Full Citation for Group Picture
PIC/5989/190 LOC Album 1094/2
Group portrait of G.P. Whitley, T.A. Everitt, A.J. Moran, Tom Iredale and Alex Chisholm, March 1950 [picture].
1950. 1 photograph : b&w ; 14 x 8.5 cm.
Part of G.M. Mathews collection of portraits of ornithologists [picture]. 1900-1949.

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